Attenuation of Insulin Action by an Allosteric Insulin Receptor Antibody in Healthy Volunteers.

Background: XOMA 358 (X358) is a fully human monoclonal antibody to the insulin receptor that acts as a negative allosteric modulator of insulin signaling. It is being developed as a novel treatment of hyperinsulinemic hypoglycemia. This report describes pharmacokinetic (PK) and pharmacodynamic (PD) data from a first-in-human clinical trial.

Methods: A double-blind, placebo-controlled, single-ascending-dose study was performed with 29 healthy adult males randomized to intravenous infusion of placebo or X358 at 0.1-, 0.3-, 1-, 3-, 6-, or 9-mg/kg dose levels. The primary objective was to assess safety and tolerability, and secondary objectives included PK and PD analyses. A short insulin tolerance test (ITT) was implemented in the 3- to 9-mg/kg dose cohorts at baseline and postinfusion.

Results: There were no deaths, serious adverse events (AEs), or subject discontinuations due to AEs. There were no clinically meaningful safety findings. X358 exhibited dose-proportional PK with a half-life of 21 days. Dose-dependent elevations of circulating insulin levels, likely related to reduced insulin clearance via monoclonal antibody action at receptors, represented a sensitive biomarker of X358 exposure. X358-dependent increases in postprandial glucose levels and fasting homeostatic model assessment of insulin resistance values were observed and persisted for at least 1 week at the higher dose levels. In all the ITT cohorts, the slope for glucose lowering was substantially attenuated after X358 infusion of a similar magnitude, but with increasing duration with rising dose level.

Conclusion: Single X358 infusions were well tolerated and resulted in a dose-dependent reduction in insulin sensitivity. Clinical development of X358 in hyperinsulinemic, hypoglycemic conditions is proceeding.